diff --git a/src/gotenberg_client/_base.py b/src/gotenberg_client/_base.py
index 3ddf8d3..a9cb260 100644
--- a/src/gotenberg_client/_base.py
+++ b/src/gotenberg_client/_base.py
@@ -9,6 +9,7 @@
 from types import TracebackType
 from typing import Dict
 from typing import Optional
+from typing import Protocol
 from typing import Type
 from typing import Union
 
@@ -28,7 +29,11 @@ class UnreachableCodeError(Exception):
     pass
 
 
-class PdfFormatMixin:
+class HasFormData(Protocol):
+    _form_data: Dict[str, str]
+
+
+class PdfFormatMixin(HasFormData):
     """
     https://gotenberg.dev/docs/routes#pdfa-chromium
     https://gotenberg.dev/docs/routes#pdfa-libreoffice
@@ -39,11 +44,11 @@ def pdf_format(self, pdf_format: PdfAFormat) -> Self:
         All routes provide the option to configure the output PDF as a
         PDF/A format
         """
-        self._form_data.update(pdf_format.to_form())  # type: ignore[attr-defined,misc]
+        self._form_data.update(pdf_format.to_form())
         return self
 
 
-class PfdUniversalAccessMixin:
+class PfdUniversalAccessMixin(HasFormData):
     """
     https://gotenberg.dev/docs/routes#pdfa-chromium
     https://gotenberg.dev/docs/routes#pdfa-libreoffice
@@ -52,11 +57,11 @@ class PfdUniversalAccessMixin:
     """
 
     def enable_universal_access(self) -> Self:
-        self._form_data.update({"pdfua": "true"})  # type: ignore[attr-defined,misc]
+        self._form_data.update({"pdfua": "true"})
         return self
 
     def disable_universal_access(self) -> Self:
-        self._form_data.update({"pdfua": "true"})  # type: ignore[attr-defined,misc]
+        self._form_data.update({"pdfua": "true"})
         return self